Alum Treatment Specifications

The specifications for alum treatment can be found here. The schedule for bidder proposals and treatment will be updated to final specifications that will be posted within two weeks when project funding is secured. This request is a draft and has not yet been formally released.

Learn more about the alum treatment process and benefits

This short video from AquaTechNex shows an example of the alum treatment process on Canyon Lake in southern California. Alum application in Canyon Lake was proposed in order to remove nutrients from the water column that contribute to algal blooms in the lake. By binding phosphorus and reducing algae growth, the continued use of alum is expected to reduce nutrient cycling and associated sediment oxygen demand in the lake sediments. The goal is compliance with the interim and final chlorophyll a TMDL targets. Alum application is also anticipated to indirectly increase dissolved oxygen in the hypolimnion as well as reduce the frequency of ammonia toxicity.

October Harvesting Postcard

Black Lake Special District

To: Black Lake waterfront property owner

Weed Harvesting
Our permit for weed harvesting was finally approved on 9/16, 64 days after the start of the approval process. At this late date, we will not proceed with harvesting as the Najas (or water nymph) will be dormant within the next few days. The permit does allow us to harvest from 7/1 to 9/30 for the next five years. We are also allowed to cut and remove the fragrant white water lily during the same cutting period. You can see the full permit and its provisions at

Blue-Green Algae
A work group is forming to look into solutions for algae blooms. If you would like to participate please email us at or call (360) 867-8814.

Letters of Concern
A letter has been sent to Thurston County expressing concern about the maintenance of the Black Lake Ditch. The ditch is becoming choked with vegetation and beaver dams have reappeared. Flooding of lower elevation properties can occur this winter.

Fish Pond Creek, a major water source to Black Lake, is reported to have high levels of fecal coliform. A letter was sent to Thurston County and the City of Tumwater; we want to better understand the problem and what is or can be done.________________________________________

Back Lake Algae Sampling, Testing and Health Alert Advisories as of October 2014

Back Lake Algae Sampling, Testing and Health Alert Advisories
as of October 2014
Sue Davis with Thurston County’s Environmental Health described the processes as follows:
* Thurston County is required to follow the Washington Department of Health testing and alert
* When Environmental Health is contacted about an algae bloom, staff take samples in areas with the
highest concentrations of algae.
* The samples are FedEx’ed to a lab in King County. Results are made available in 5 days. The delay
is largely due to the testing process. If the sample shows harmful toxin levels, a Health Alert Advisory
is published.
* Samples are taken and tested once a week following a health alert. When two successive weeks
show toxin levels to be safe (or algae has dissipated), the Health Alert Advisory is lifted.
* The minimum period for a Health Alert Advisory is usually 3 weeks.
* Many areas of the lake where algae is not present are safe during a Health Alert Advisory.
* Areas of the lake with algae should be avoided even when a Health Alert is not in effect.
* Algae testing results for Washington lakes can be found at: